1. Field
The present invention relates generally to communications, and more specifically to a novel and improved method and apparatus for performing KASUMI ciphering.
2. Background
Wireless communication systems are widely deployed to provide various types of communication such as voice, data, and so on. These systems may be based on code division multiple access (CDMA), time division multiple access (TDMA), or some other modulation techniques. A CDMA system provides certain advantages over other types of systems, including increased system capacity.
A CDMA system may be designed to support one or more CDMA standards such as (1) the “TIA/EIA-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), (2) the “TIA/EIA-98-C Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the IS-98 standard), (3) the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), (4) the standard offered by a consortium named “3rd Generation Partnership Project 2” (3GPP2) and embodied in a set of documents including “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A Upper Layer (Layer 3) Signaling Standard for cdma2000 Spread Spectrum Systems,” and the “C.S0024 cdma2000 High Rate Packet Data Air Interface Specification” (the cdma2000 standard), and (5) some other standards. A system that implements the High Rate Packet Data specification of the cdma2000 standard is referred to herein as a high data rate (HDR) system. The HDR system is documented in TIA/EIA-IS-856, “CDMA2000 High Rate Packet Data Air Interface Specification”. Proposed wireless systems also provide a combination of HDR and low data rate services (such as voice and fax services) using a single air interface.
Encryption techniques are commonly used to provide security for transmitted data, and to provide authentication for users attempting to access data. Encryption is used in a variety of fields, and is particularly useful for digital wireless communication systems.
One encryption algorithm, specified for use in the W-CDMA standard, is KASUMI. KASUMI is detailed in “Document 2: KASUMI Specification”, of the ETSI/SAGE Specification “Specification of the 3GPP Confidentiality and Integrity Algorithms”, version 1.0, dated Dec. 23, 1999 (hereinafter the KASUMI specification). Various uses of KASUMI are detailed in the same ETSI/SAGE specification, in “Document 1: f8 and f9 Specification”. KASUMI is a block cipher that produces a 64-bit output from a 64-bit input utilizing a 128-bit key. The output of KASUMI can be used as a keystream to encrypt data, commonly by taking the exclusive-or (XOR) of bits of the keystream with bits of the data to be encrypted.
It is common in the art for communication systems to employ ASICs or other hardware solutions to implement various sub-functions thereof. In ASIC design, smaller utilized area translates to lower costs, higher yields, and often lower power. Low cost and power is beneficial in both fixed and mobile applications, but low power is particularly important in mobile devices which utilize batteries. At the same time, processing must be completed within certain time limits. Wireless data systems, such as W-CDMA systems, will need to incorporate KASUMI implementations into their subscriber and base stations, and designers will need to work within various constraints including those just described. As such, there is a need in the art for an apparatus or method that performs KASUMI ciphering in an efficient manner.